Method of setting printing inks and composition therefor



-' 106, COMPOSITIONS,

COATING OR PLASTIC Patented Apr. 27, 1943 s 7:

CROSS REFERENCE METHOD OF SE'ITING PRINTING INKS AND COMI'OSITIONTHEREFOR charles qeese, Somerton, Pa.

No Drawing. Application June 13, 194 Serial No.340,338

The invention relates to printing, and more particularly to the methodof accelerating 'the drying of printing inks immediately after they havebeen transferred to the material to be printed upon. More particularlythe invention relates to the use of liquid sprays which I havediscovered are very beneficial in connection with the drying of printinginks. I

In high speed printing presses a long recognized obstacle to obtaininguniform high grade printing has been the difficulty of drying the-inkfast enough to prevent the oilsetting or smearing of ink from freshly.printed sheets or webs, as, for example, paper, during the steps whichimmediately follow the printing steps, namely, during the piling of thesheets or the folding or winding of printed webs. The condition thusproduced is commonly known as offset.

The methods and expedients to overcome' this undesirable condition thathave been commonly adopted in the printing art have not beenidirooted toattacking the source of the difiiculty, namely, the slowness in dryingofthe printing inks, but have more or less accepted that condition andhave sought means of eliminating the undesirable results of the existingconditionproduced by relatively slow drying inks. The makeshift methodof preventing the smearing of. the slow drying inks has been to deposit,as by spraying, a multitude of minute particles upon the freshly printedsheets or webs, the particles serving in effect as small projectionsupon the:surface of the sheet and spacing the sheets orportions of thewebs sufliciently apart so that the ink from one sheet or web will notbe transferred to an adjacent sheet or portion of the web. Varioussubstances, both in dry -or solution form, have been employed as theofiset preventing;particles. For example, such substance aswax,-cellulos e derivatives and clay, tal c and the like, we

been employed as showif'ii'i the Young Patent No. 2,114,792, the BucyPatent No. 2,0'78,' 790, and the Grammer Patent;l Io,'- 1,445,273.Obviously, these methods are merelymakeshift expedients withoutattacking thebasic dimculty, namely, of accelerating drying of theljnkand in themselves frequently smear or gumup the"printed, sheets and themoving parts of the printing'press.

The primary object of the present inyention the printing ink isimmobilized and the smearing is to attack the basic difficulty' of theoffsetting'efio of the ink is prevented and the effective drying orsetting thereof is accelerated.

It has been found particularly essential in the practice of theinvention that in spraying any of the solutions which I have found to besatisfactory on the freshly printed sheets or web the solution orsuspension be in very finely-divided form. An excess of the solution inany spot or area is as objectionable as is a deficit of the solution. Insprays containing numerous liquid particles of relatively largediameter, the heavy particles not only tend to deposit at adisproportionate rate; but it is impossible to maintain a'uniform'density of liquid'in the air above the sheet or web to besprayed, and irregular and uncontrollable results are obtained. It ispreferred that the particles be kept of approximately 50 microns indiameter or smaller, and it has been found that the spray of thesolution of that order may be deposited readily and uniformly on thefreshly printed sheets or webs.

The invention may'be employed to facilitate the setting of any of thevarious types of printing ink,'in cluding the oil or varnish base inksand the cellulose base inks, and the invention may be employed ingeneral'letterpress printing such as fiat-bed or rotary pressesincluding newspaper presses and color printing as well asoffsetlithographic printing. I

Particular solutions which I have found satisfactory are the alkalinesilicates which are soluble in water and whi'cfiihhy be employed with orwithout modifiers. For example, aqueous solutions of sodium silicate andpotassium silicate have been oun par icularly suitable. e solution ispreferably applied to the freshly printed paper in the finely dividedform described just after it emerges from the printin cylinders and asit is passing over the delivery mechanism.

Any suitable spraying means may be employed, for example, a liquidatomizing device adapted to spray the solution in the form of a finelydivided mist. The spraying mechanism may comprise one or a plurality ofspraying -n0zzles preferably disposed above the printed sheet andadapted to spray downwardly in such manner that a continuous and evenfilmis formed on the entire printed surface; the number of sprayingnozzles employed is dependgntajupon the width of the "printed' sheet orweb,'the number being suflicient so that fthe entire width of the sheetis covered. The spraying mechanism is preferably enclosed in a hoodinorder that the spray may not escape and spread through the pressroom.

The concentration of the silicate in the aque- Examiner ous solution mayvary within rather wide limits, depending upon the type of printing andthe nature of the paper employed, for example, in printing on newspaperstock in a rotary web press a satisfactory solution to be sprayed uponthe freshly printed web may comprise approximately -12 sodium silicate,in offset printing an aqueous so ution comprising sodium silicate as'eefi round satisfactory, and in general letterpress printing such as onfiat beds and printing on cartons a solution comprising 50% sodiumsilicate has been found to be suitable. The concentration of thesolution has an important bearing on the character of the drying action,since if the solution is extremely dilute it will not set fast enoughafter being sprayed upon the freshly printed paper, and if it isextremely concentrated it will set too rapidly and before the solutionhas properly penetrated the paper fibres and formed a continuous film.

When the silicate solution is sprayed in the form of a mist on thefreshly printed paper, a very thin film is formed over the printedsurface which penetrates to some extent into the fibres of the paper. agel forming a glaze over each fibre and between the surface fibres.Since the layer of ink on the freshly printed paper is quite thin, italso is absorbed into the surface fibres of the paper and it is believedthat there is some intermingling or interaction of the ink and thesilicate in the paper fibre so that, when the silicate sets into a gel,the ink will be immobilized and held quite firmly in place. Even wherethe ink deposit on the sheet is fairly heavy as in solids, it is fairlywell surrounded with the silicate gel since the silicate solutionpenetrates into the paper fibres very rapidly. Evaporation of thesolvent continues .for some time after the silicate gel has formed onthe printed surface and within the paper fibres, and the resultingsurface gel or glaze is quite porous so that oxygen may readilypenetrate it and accentuate the normal process 01 the drying of the ink.As previously set forth, the alkaline silicates are preferred since themore alkaline the silicate the greater is the wetting power or degree ofpenetration of the solution into the paper fibres, whereas the lessalkaline silicates will tend to set faster.

After the solution has been sprayed on the freshly printed paper, theevaporation of the solvent may be accelerated by heating the sheet bymeans of a gas flame under the sheet, such as is now the standardequipment on numerous printing presses, or by any other suitable heatingelement.

In view of the porosity of the silicate gel on the freshly printedsurface, a second layer of ink may be readily printed thereon, as incolor printing, and the process of printing and then spraying with thesilicate solution may be repeated quite a number of times with satisfac-The solution then sets to tory results. Furthermore, if desired, a filmof a silicate solution may be applied to the paper before it has beenprinted upon.

A modification of the method contemplates the inclusion of a smallpercentage of watersoluble or water-dispersible wax in the silicatesolution. For example, four ounces of a watersoluble or waterdispersible wax may be dissolved in a gallon of a 20% solution of sodiumsilicate.

An important feature of the method is the fact that fine printing can beobtained with less expensive inks in that it is not necessary to employwith my method printing inks having expensive volatile solvents anddriers.

I claim:

"1. The method of setting printing ink comprising applying an alkalinesilicate solution in finely divided form to a freshly printed surface.

2. The method of setting printing ink which comprises spraying asolution of a water-soluble silicate upon a freshly printed surface. 3.The method of setting printing ink comprising applying a thin film of anaqueous solution of sodium silicate in finely divided form to a freshlyprinted surface.

4. The method of setting printing ink comprising applying a thin film ofan aqueous solution of potassium silicate in finely divided form to afreshly printed surface.

5. The method of setting printing ink which comprises applying to afreshly printed surface a'thin film of an aqueous solution of analkaline silicate in finely divided form and heating said printedmaterial to accelerate the evaporation of the solvent.

6. The method of printing which comprises applying a film of an aqueoussolution of an alkaline silicate in finely divided form to the surfaceof material to be printed upon just prior to the time printing ink isapplied to said surface.

7. The method of setting printing inks cornprising applying a thin filmof an aqueous solution of :an alkaline silicate and a small proportionof a water soluble or water dispersible wax in finely divided form to afreshly printed surface.

8. A composition of matter for setting printing inks which may beapplied to a freshly printed surface in finely divided form, comprisingan aqueous solution of an alkaline silicate having relatively highwetting power and adapted to rapidly penetrate the paper fibres, saidalkaline silicate comprising 10-50% of the solution.

9. A composition of matter for setting printing inks, which may besprayed upon a freshly printed surface in finely divided form,comprising an aqueous solution having a major proportion of an alkalinesilicate and minor proportions of a water-soluble wax.

CHARLES GEESE.

